A source for any tile server with a URL template.

source: {StaticMaps.Source.Template,
         url: "https://{s}.tiles.example.com/{z}/{x}/{y}{r}.png?key=…",
         subdomains: ~w(a b c),
         attribution: "© Example Maps"}

Placeholders

• {z}, {x}, {y} — the tile
• {-y} — the row counted from the south, for TMS servers
• {s} — a subdomain from :subdomains, chosen from the tile so a tile always has the same URL
• {r} — "@2x" for a high-density tile, "" otherwise

Mirrors

:url may be a list of templates for servers that serve identical tiles, such as your own tile servers:

url: ["https://tiles1.example.com/{z}/{x}/{y}.png",
      "https://tiles2.example.com/{z}/{x}/{y}.png"]

Each tile goes to a mirror chosen from its position, so a tile always has the same URL and the load spreads evenly. If that mirror fails, the tile is fetched from the next one, and so on; a 404 is not retried elsewhere, since the tile does not exist.

:max_concurrency is the limit for the source as a whole, across all its mirrors. A per-mirror limit cannot hold during failover: while one mirror is down, its tiles go to the others, which would then see their own share and the dead mirror's at once. With one limit, no mirror ever sees more than :max_concurrency requests, so raise it by the number of mirrors if each can take the full amount.

Mirrors must serve the same tiles. Different providers draw different maps, and mixing their tiles makes a patchwork; for a different provider as a backup, use a fallback source instead: source: [primary, fallback].

Options

• :url — the template, or a list of mirror templates; required
• :attribution — required
• :tile_size — 256 (default) or 512
• :zoom — the tile zooms the server serves, default 0..19
• :scales — default [1, 2] when the template has {r}, else [1]
• :subdomains — required when the template has {s}
• :max_concurrency — requests in flight at once, across all mirrors; default 8
• :cache — false keeps these tiles out of the tile cache, for providers whose terms forbid server-side caching; default true. guides/tile-providers.md says which providers need it.